Lamp reflector assembly

ABSTRACT

A lamp assembly having a reflector holding a lamp element, or burner. A reflector extension is designed to mate to the reflector. The reflector extension has a first open end toward the reflector. The first open end typically is in contact with the reflector to form a seal around the perimeter preventing glass shards from escaping between the reflector and reflector extension. The second end of the reflector extension also is open to allow the light from the arc to exit the reflector extension. A transparent plate placed across this second open end prevents glass from leaving the reflector extension. The transparent plate typically is glass, and may have an antireflective coating applied to the plate to limit the light reflected by the plate. Ventilation ports in the reflector extension allow cooling airflow into the cavity around the burner.

This application claims priority under 35 U.S.C. § 119(e)(1) ofprovisional application number 60/250,522 filed Nov. 30, 2000.

FIELD OF THE INVENTION

This invention relates to the field of display systems, moreparticularly to display systems using high pressure lamps, moreparticularly to reflectors and housings for high pressure lamps.

BACKGROUND OF THE INVENTION

Projection display systems have improved dramatically over the lastdecade. The color gamut and purity has improved at the same timeremarkable improvements in resolution and image brightness have alsobeen made. On top of these changes, the size, weight, and cost of theprojectors have fallen dramatically. These improvements have led toentirely new markets for the projectors. For example, mobileprofessionals are now able to carry their own projectors topresentations to ensure compatibility between their portable computerand the display projector. These portable computers weigh less thanthree pounds, yet produce excellent images even in relatively brightenvironments.

In spite of the very small size and weight of the state of the artprojectors, consumers desire even smaller and lighter projectors.Producing further reductions in size and weight have been challenging.The optical components are difficult to shrink. Of special concern isthe arc lamp. The arc lamp is comprised of two electrodes in a glassampoule. This glass ample contains a gas that is heated to a plasma bythe arcing between the electrodes. A reflector collects the light fromthe plasma and focuses the light into the aperture of the illuminationoptics of the display.

Explosion is a common failure mode of arc lamps. The force of theexplosion is quite strong, and the glass shards created by the explosionmust be contained within the projector. Without containment, the glassshards easily can damage optical components in the projector or becomelodged in the other electrical and mechanical components. The glassshards must also be prevented from exiting the projector case. A glassplate, thick enough to stop the glass shards created by the explosion ofthe lamp, typically is placed over the end of the reflector to containthe explosion. Unfortunately, this glass plate interferes with the airflow intended to cool the arc lamp.

The arc lamp creates a tremendous amount of heat, much of it in longwave infrared energy. The infrared energy cannot pass through the glassplate and creates an unfavorable thermal environment for the arc lamp.Specifically, the excess temperature leads to oxidation of theelectrodes and devitrification of the lamp wall materials. Thus, theexcess heat reduces the life of the arc lamp. One way to reduce the heatis to enlarge the size of the reflector to increase the space betweenthe arc and the reflector wall. Unfortunately, enlarging the reflectorlimits how small the projector can be. What is needed is a method ofcooling the burner that does not enlarge the size of the projector.

SUMMARY OF THE INVENTION

Objects and advantages will be obvious, and will in part appearhereinafter and will be accomplished by the present invention whichprovides a method and system for lamp reflector assembly that providessufficient cooling even for very small reflectors. One embodiment of theclaimed invention provides a reflection extension. The reflectorextension comprises a reflector extension body and a transparent plate.The reflector extension body has a first open end and a second open end.The reflector body is formed to receive light from a light source in areflector. The first open end is formed to receive the reflector, andthe second open end is arranged to allow the light from the light sourceto pass through. The transparent plate is positioned to cover the secondopen end of the reflector extension.

Another embodiment of the present invention provides a lamp assembly.The lamp assembly comprises: an arc lamp, a reflector, a reflectorextension, and a transparent plate. The reflector is positioned tocapture and reflect light from the arc lamp. The reflector extension hasa first open end to receive light from the arc lamp and reflector, and asecond open end arranged to allow the light from the arc lamp andreflector to pass through. The transparent plate positioned to cover thesecond open end of the reflector extension.

Another embodiment of the current invention provides a lamp assembly.The lamp assembly comprises: an arc lamp, a reflector, a taperedreflector extension, and a transparent plate. The reflector ispositioned to capture and reflect light from the arc lamp. The taperedreflector extension has a first open end to receive light from the arclamp and reflector, and a second open end arranged to allow the lightfrom the arc lamp and reflector to pass through. The transparent plateis positioned to cover the second open end of the tapered reflectorextension. Together, the reflector, tapered reflector extension, andtransparent plate enclose the arc lamp.

Yet another embodiment of the present invention provides a displaysystem. The display system comprises: a lamp assembly, a spatial lightmodulator, a controller, and a projection lens. The lamp assemblycomprises: an arc lamp, a reflector, a tapered reflector extension, anda transparent plate. The reflector is positioned to capture and reflectlight from the arc lamp. The tapered reflector extension has a firstopen end to receive light from the arc lamp and reflector, and a secondopen end arranged to allow the light from the arc lamp and reflector topass through. The transparent plate is positioned to cover the secondopen end of the tapered reflector extension such that the reflector,tapered reflector extension, and transparent plate enclose the arc lamp.The spatial light modulator is in the light path and operable tomodulate the light beam according to image data received by the spatiallight modulator. The controller provides the image data to the spatiallight modulator. The projection lens focuses the modulated light beamonto an image plane. The display system typically includes othercomponents such as illumination relay optics, color filters, and coolingfans.

The disclosed invention improves access for cooling the arc lamp toprolong the life of the lamp and contains lamp explosions without damageto the rest of the display system. The cooling and containment isaccomplished using a reflector extension positioned in what isnecessarily dead space in the projector. The improved cooling allows theuse of smaller lamp reflectors-shrinking the size of the display system.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 is an exploded perspective view of a lamp assembly according tothe present invention.

FIG. 2 is a cross section side view of a lamp assembly according to oneembodiment of the present invention.

FIG. 3 is a cross section side view of a lamp assembly according toanother embodiment of the present invention.

FIG. 4 is a cross section side view of a lamp assembly according to thepresent invention having optional cooling vents molded into thereflector extension.

FIG. 5 is an end view of the lamp assembly of FIG. 4 showing controlledsurfaces used to align the lamp assembly with the display projector.

FIG. 6 is a cross section perspective view of a lamp assembly accordingto the present invention having an optional electrical connection formedin the lamp extension.

FIG. 7 is a schematic diagram of a display system using the improvedlamp assembly of the current invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A new lamp assembly has been developed that improves the cooling of thelamp while protecting users of the lamp from explosions, yet allows theuse of smaller reflectors and fewer parts to reduce the overall size ofthe display systems.

FIG. 1 is a cross section perspective view of a lamp assembly accordingto one embodiment of the present invention. In FIG. 1, a reflector 102contains the lamp element, or burner 104. The burner has an electrodeextending from each end and a chamber 106 in the middle in which the arcand plasma are contained. The reflector 102 typically is an ellipse,with the arc positioned at one foci of the ellipse. An ellipticalreflector is preferred since it focuses the light from the arc withoutrequiring a condenser lens.

A reflector extension 108 is designed to mate to the reflector 102. Thereflector extension 108 has a first open end toward the reflector 102.The first open end typically is in contact with the reflector 102 toform a seal around the perimeter preventing glass shards from escapingbetween the reflector 102 and reflector extension 108. Preferably, thereflector extension 108 contacts the reflector 102 around the perimeterof the reflector 102.

The reflector extension 108 need not make contact with the reflector 102around this perimeter. For example, the first open end of the reflectorextension 108 could be larger than the reflector 102, allowing thereflector extension to extend beyond the end of the reflector 102. Theoverlap between the reflector extension 108 and the reflector 102provides a baffle to stop glass shards.

The second end of the reflector extension 108 is also open. The secondopen end allows the light from the arc to exit the reflector extension108. A transparent plate 110 is placed across this second open end toprevent glass shards from leaving the reflector extension 108. Thetransparent plate 110 typically is glass, and preferably is a flat glassplate that does not interfere with the light traveling through thereflector extension. The transparent plate 110 may have anantireflective coating applied to the plate to limit the light reflectedby the plate 110. The plate may be perpendicular to the axis of thereflector, or tilted at an angle to it.

FIG. 1 also shows two ventilation ports 112 that allow cooling airflowinto the cavity around the burner 104. These ventilation ports can alsobe formed by a series of small holes or slots in the reflector extension108. The size of the holes or slots preferably are small enough toprevent large glass shards from passing through the holes. When largeventilation ports 112 are used, the flange around the ventilation portstops the glass shards such that the glass leaves the reflectorextension 108 at a very low velocity if at all. The openings, whetherholes, slots, or ports, typically are designed so that no shard from thechamber 106 can have a direct path outside the lamp assembly. Thus, anyshards must collide with the reflector or reflector extension and giveup much of their kinetic energy before exiting the lamp assembly.

FIG. 2 is a cross section side view of another embodiment of thereflector extension 202. The converging rays of light 204 shown in FIG.2 illustrate how the reflector 102 focuses the light from the burner104. These rays converge to a point 206 on the optical axis of thereflector. The next optical component, typically a color wheel orintegrating rod, is located at the point of convergence 206.

The conical volume defined by the converging rays must be kept free ofany projector components. Therefore, almost all of the volume used bythe reflector extension 202 would be dead space in a projector evenwithout the reflector extension 202. FIG. 2 shows a reflector extension202 having a straight taper to the second open end. The straight taperminimizes the amount of space consumed by the reflector extension 202,and simplifies its construction.

The reflector extension 202 must be long enough to allow the projectorto cool the burner 104. If the reflector extension 202 is too short, thevolume enclosed by the reflector 102 and reflector extension 204 willnot allow proper air circulation. Furthermore, the limited surface of ashort extension makes it difficult to provide enough ventilation. Alonger reflector extension 202 provides much better control of thetemperature inside the reflector. The longer the reflector extension202, the more air inside the reflector enclosure and the easier it is toadd vents to the extension. A longer reflector extension 202 alsoprovides a greater surface area through which to conduct heat away fromthe burner 104.

Because the reflector extension is tapered, a longer extension requiresa smaller transparent plate to cover the second open end. The smallertransparent plate lowers the cost and weight of the system. The smallertransparent plate allows the use of ultraviolet or infrared rejectioncoatings because the coatings will cost less to form on the smallersurface. Furthermore, because the reflector extension moves thetransparent plate near the focal point of the primary reflector,limiting the ability of the transparent plate to reflect energy to afocal point near the burner avoiding a thermal load on the burner due tothe reflected light.

FIG. 3 is a cross section side view of a second embodiment of areflector extension 302. The reflector extension 302 of FIG. 3 has acurved taper, such as another ellipse. This curved taper is intended tobetter reflect incident light to the primary reflector 102. The insideof the reflector extension 302 optionally has a reflective coatingapplied to the inner surfaces. The various shapes and coatings appliedto the reflector extensions according to this invention enable thereflector extension to reflect light back to the primary reflectorand/or into the aperture of the remaining optical system—typically anintegrating rod is the next component in the display system.

One embodiment of a reflector extension 302 with a curved taper placesthe second focal point at the arc. Light traveling directly from the arcto the reflector extension 302 will reflect from the reflectorextension, pass through the first focus point of the reflectorextension, and return to the arc. Ideally, after passing through the arcthe light will be focused by the primary reflector 102 onto the secondfocus point of the primary reflector 102 which is the aperture of theremaining optical system.

As with all embodiments described herein, the reflector extension 302 ofFIG. 3 can have a complex taper. For example, a reflector extension mayuse two different tapers, or a curved section and a straight section.

FIG. 4 is a cross section side view of the lamp assembly including thereflector extension 108 of FIG. 1. The reflector extension 108 of FIG. 4has a straight taper and two ventilation ports 112. The reflectorextension 108 of FIG. 4 also includes alignment surfaces 114. Thealignment surfaces 114 are used to align the reflector extension 108with the display system chassis. The reflector extension 108 of FIG. 4uses four alignment surfaces, but the number of alignment surfaces isnot critical. For example, three alignment surfaces are all that areneeded to define an alignment plane.

FIG. 5 is an end view of the reflector extension 108 of FIG. 4. Thelocation of the four alignment surfaces is clearly shown in FIG. 5. Thereflector extension 108 typically is a metal or plastic material thatcan be formed with more elaborate features compared to glass structures.As mentioned above, these alignment surfaces provide preciseregistration between the display system chassis and the reflector 102.

The lamp assembly comprising the reflector extension 108, reflector 102,and burner 104 typically are manufactured as a single user replaceableunit. During the assembly of the lamp assembly, the lamp manufacturerjoins the reflector 102 and reflector extension 108, which typicallyhave a mechanical means of alignment formed in the reflector 102 andreflector extension 108 to ensure the reflector and reflector extensionshare the same optical axis. The lip shown in FIG. 4 is one example of asuitable mechanical means of alignment. The alignment means also may bekeyed to ensure the reflector and extension are not rotated relative toone another.

After the reflector 102 and reflector extension 108 are assembled, theyare held in place using the alignment surfaces 114 while the burner 104is installed in the reflector 102. The burner 104 is moved within thereflector 102 to place the arc at a first focus point of the reflector.Once aligned, the burner 104 is potted in place to prevent it frommoving. Thus, all three components of the lamp assembly are manufacturedto be in alignment with the alignment surfaces formed in the reflectorextension.

FIG. 6 is a cross section perspective view of the lamp assembly showingan optional electrical connection 604 through the reflector extension602 to one electrode of the burner 104. The other electrode 606 of theburner 104 is connected through the primary reflector 102. As mentionedabove, the use of metal or plastic to form the reflector extensionallows more intricate molding of the reflector extension and easilyaccommodates molding in the burner electrical connection.

The various embodiments of the reflector extension described abovetypically are formed from either plastic or metal. Metal reflectorextensions provide the advantage of better thermal conductivity. Plasticreflector extensions provide the advantage of electrical insulation.Multi-shot processes, or separate pieces, can be used to provide athermally conductive, yet electrically insulative reflector extension.

FIG. 7 is a schematic view of an image projection system 700 using animproved lamp assembly 702 according to the present invention. In FIG.7, light from the lamp assembly 702, as described above, is focused ontoa color wheel 704. The color wheel spins to provide sequential primarycolored beams of light to an integrator rod 706. The integrator rod 706homogenizes the light to provide uniform illumination across the entiresurface of a spatial light modulator 708. In practice, other relayoptics, such as lenses, mirrors, and prisms, are used to gather,control, and focus the light from the lamp assembly onto the spatiallight modulator. Likewise, additional mechanical components such ascooling fans or blowers may be used to provide cooling air flow to thelamp assembly, typically through the openings in the reflector extensiondescribed above.

optical components The spatial light modulator 708, typically amicromirror or liquid crystal device, spatially modulates the beam oflight according to image data provided by a controller 710. Themodulated light is then focused by a projection lens 712 onto an imageplane 714. Alternatively, a color splitting prism is substituted for thecolor wheel 704, and three spatial light modulators 708 are used. Thecolor splitting prism separates the white light from the lamp assembly702 into three primary colored light beams. Each primary colored lightbeam is modulated by a separate spatial light modulator 708.

Thus, although there has been disclosed to this point a particularembodiment for an improved reflector assembly and method therefore, itis not intended that such specific references be considered aslimitations upon the scope of this invention except insofar as set forthin the following claims. Furthermore, having described the invention inconnection with certain specific embodiments thereof, it is to beunderstood that further modifications may now suggest themselves tothose skilled in the art, it is intended to cover all such modificationsas fall within the scope of the appended claims.

1. A reflector extension comprising: a reflector extension body having afirst open end and a second open end and at least one cooling vent, saidfirst open end formed to receive light from a said reflector, saidsecond open end arranged to allow said light from said reflector to passthrough; and a transparent plate, said transparent plate positioned tocover said second open end of said reflector extension.
 2. The reflectorextension of claim 1, said reflector extension body comprising a taperedextension body.
 3. The reflector extension of claim 2, said taper beinga straight taper.
 4. The reflector extension of claim 2, said taperbeing a curved taper.
 5. The reflector extension of claim 1, saidreflector extension body having a reflective inner surface.
 6. Thereflector extension of claim 1, said reflector extension comprising aplastic reflector extension body.
 7. The lamp assembly of claim 1, saidreflector extension comprising a metal reflector extension body.
 8. Thereflector extension of claim 1, further comprising: at least two coolingvents formed in said reflector extension body.
 9. The reflectorextension of claim 1, said reflector extension further comprising: anelectrical connection between an exterior surface of said reflectorextension and a light source.
 10. The reflector extension of claim 1,further comprising: at least one alignment surfaces to position saidreflector extension within a display systems.
 11. The reflectorextension of claim 1, said reflector extension body formed to receivesaid reflector.
 12. The reflector extension of claim 1, said reflectorextension body formed to locate said reflector.
 13. The reflectorextension of claim 1, said reflector extension body formed to align saidreflector.
 14. The reflector extension of claim 1, said reflectorextension body formed to receive said reflector.
 15. The reflectorextension of claim 1, said reflector extension body formed to locatesaid reflector.
 16. The reflector extension of claim 1 , said reflectorextension body formed to align said reflector.
 17. A reflector extensioncomprising: a reflector extension body having a first open end and asecond open end, said first open end formed to receive light from areflector, said second open end arranged to allow said light from saidlight source to pass through, said reflector extension body having atleast one alignment surface to position said reflector extension withina display system; and a transparent plate, said transparent platepositioned to cover said second open end of said reflector extension.18. The reflector extension of claim 17, said reflector extension bodycomprising a tapered extension body.
 19. The reflector extension ofclaim 18, said taper being a straight taper.
 20. The reflector extensionof claim 18, said taper being a curved taper.
 21. The reflectorextension of claim 17, said reflector extension body having a reflectiveinner surface.
 22. The reflector extension of claim 17, said reflectorextension comprising a plastic reflector extension body.
 23. The lampassembly of claim 17, said reflector extension comprising a metalreflector extension body.
 24. The reflector extension of claim 17,comprising: at least one cooling vent formed said reflector extensionbody.
 25. The reflector extension of claim 17, further comprising: atleast two cooling vents formed in said reflector extension body.
 26. Thereflector extension of claim 17, said reflector extension furthercomprising: an electrical connection between an exterior surface of saidreflector extension and a light source.
 27. The reflector extension ofclaim 17, further comprising: at least two alignment surfaces toposition said reflector extension within a display system.